1. Field of the Invention
The present invention relates to procedures and equipment for maintaining waste water treatment systems. In particular, the present invention relates to an apparatus for maintaining the operating effectiveness and efficiency of a rotary screen thickener cleaning shower.
2. Description of the Prior Art
Rotary screen thickeners are devices for primary separation of water and solids from a waste water treatment facility. Influent to a rotary screen thickener is a pumpable, 3 to 10 percent solids consistency, sludge from the bottom of a settling basin. To further increase the solids content of the sludge, water is removed through the mesh openings of a finely woven screen. Particulate solids larger than the mesh openings are retained on the screen surface.
These screens are formed as cylindrical walls about a circular framework that is rotatively driven about a cylindrical axis. A ribbon baffle helically follows the inner screen surface to advance the sludge flow along the cylinder from the influent to discharge ends as the cylinder rotates. At the discharge end, the cylinder wall is open to permit the thickened sludge to fall into a funnel opening through the outer shell of the unit.
To keep the screen openings clear of accumulated fiber and particulates, the screen is showered with water: frequently from a recycle tank. Although recycled shower water is burdened with substantially less particulate matter than the influent sludge, recycle water still has a significant solids and fibrous content. This residual solid and fiber tends to obstruct the shower orifices at the nozzle entrance inside the shower distribution manifold.
In anticipation of this operational difficulty, brushes have been integrated with the shower manifold assembly having bristles projecting radially from an axially positioned rod which extends the length of the manifold. At one end of the manifold, the brush rod penetrates the manifold enclosure to receive a hand wheel by which the brush may be rotated to clean such accumulated debris away from the nozzle openings.
Due to the physical size of rotary screen units and where they are located in a waste water treatment plant, manual cleaning may impose unreasonable burdens on the plant operators. Continuous motorized rotation of the brush is also unacceptable due to interference with water flow within the manifold and consequential equipment wear.
It is also desirable that the dislodged debris, much of it being too large to pass through the nozzle orifices, be purged from the manifold interior. For this purpose, a purge valve is provided in the manifold conduit at the opposite axial end from the spray water inlet. When the nozzle cleaning brush is rotated, the purge valve is opened to flush the manifold channel.
At least one supplier of such equipment has integrated the nozzle cleaning brush with the purge valve so that rotation of the brush hand wheel also opens and closes the purge valve. Nevertheless, manual attention and action is required.
It is therefore, an objective of this invention to automate the nozzle cleaning procedure for the screen cleaning shower of a rotary screen thickener.
Another object of the present invention is to provide a selective interval time controller by which a rotary screen thickener cleaning shower may be simultaneously brushed and flushed